i could make a really intelligent reply, but salsa and this whole thread reminds me of a scene from resevoir dogs...which applies here imo. for anyone who's not seen it, first of all, just see it. second, there are eight guys out for breakfast, and as they're getting ready to leave, the one guy (played by steve buscemi, who fucking owns) goes on a whole diatribe how it's not his fault that waitresses are underpaid, and how it's not his job to tip them, etc. every one of them are supposed to fork over a buck as a tip for the waitress...

the guy who took them out for breakfast sees that he's not left a dollar, and his reply fits here...

"Cough up a buck you cheap bastard."

I'm not even saying someone should do it because it's a custom. If your server fucking sucks, then give them 15%. maybe a little less. But man, if they really put forward that extra effort, why not toss them a few extra dollars? Put yourself in their shoes. You may be in that position someday. Besides, what's an extra 1/2/3/4 dollars? Will this really affect you? However, it adds up for them. I dunno, if you're going to order food/get it delivered/etc. you should be ready to tip a reasonable amount. It's just courteous...